Chemistry (Chang), 9th EditionChapter 20:
Metallurgy and the Chemistry of MetalsChapter Summary1. Depending on their reactivities, metals exist in nature in either the free or
combined state.
2. Recovering a metal from its ore is a three-stage process. First, the ore must be
prepared. The metal is then separated, usually by a reduction process, and finally, it
is purified.
3. The methods commonly used for purifying metals are distillation, electrolysis, and
zone refining.
4. Metallic bonds can be thought of as the force between positive ions immersed in a
sea of electrons. In terms of band theory, the atomic orbitals merge to form energy
bands. A substance is a conductor when electrons can be readily promoted to the
conduction band, where they are free to move through the substance.
5. In insulators, the energy gap between the valence band and the conduction band is
so large that electrons cannot be promoted into the conduction band. In
semiconductors, electrons can cross the energy gap at higher temperatures, and
therefore conductivity increases with increasing temperature as more electrons are
able to reach the conduction band.
6. n-Type semiconductors contain donor impurities and extra electrons. p-Type
semiconductors contain acceptor impurities and “positive holes.”
7. The alkali metals are the most reactive of all the metallic elements. They have an
oxidation number of + 1 in their compounds. Under special conditions, some of
them also form uninegative ions.
8. The alkaline earth metals are somewhat less reactive than the alkali metals. They
almost always have an oxidation number of + 2 in their compounds. The properties
of the alkaline earth elements become increasingly metallic from top to bottom in
their periodic group.
9. Aluminum does not react with water due to the formation of a protective oxide; its
hydroxide is amphoteric.  | 
